532 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



lemma about 4 mm. long, the others obsolete. 01 — Plains and dry 



successively shorter, the middle awns woods, southern Texas and Mexico; 



of all 5 to 15 mm. long, somewhat southern South America, 

 spreading, the lateral awns short or 



112. BOUTEL0UA Lag. Grama 



Spikelets 1-flowered, with the rudiments of 1 or more florets above, sessile, 

 in 2 rows along one side of the rachis; glumes 1-nerved, acuminate or awn- 

 tipped, the first shorter and narrower; lemma as long as the second glume or a 

 little longer, 3-nerved, the nerves extending into short awns or mucros, the 

 internerves usually extending into lobes or teeth; palea sometimes 2-awned; 

 rudiment various, usually 3-awned, the awns usually longer than those of the 

 fertile lemma, a second rudimentary floret sometimes present. Perennial or 

 sometimes annual, low or rather tall grasses, with 2 to several or many spikes 

 racemose on a common axis, or sometimes solitary, the spikelets few to many 

 in each spike, rarely solitary, pectinate or more loosely arranged and appressed, 

 the rachis of the spike usually naked at the tip. The sterile florets forming the 

 rudiment are variable in all the species and commonly in individual specimens. 

 The general pattern of rudiment is fairly constant for each species, the vari- 

 ability being in the reduction or increase in number and size of the sterile 

 florets, the reduction from 3 awns to 1, and in the amount of pubescence. 

 Type species, Bouteloua racemosa Lag. (B. curtipendula). Named for the broth- 

 ers, Boutelou, Claudio, and Esteban. The genus was originally published as 

 Botelua. 



The many species are among our most valuable forage grasses, forming an 

 important part of the grazing on the western ranges. B. gracilis, blue grama, 

 and B. hirsuta, hairy grama, are prominent in "short grass" regions of the 

 Great Plains; B. eriopoda, black grama, and B. rothrockii, Rothrock grama, 

 are prominent in Arizona. Two annuals, B. barbata and B. parryi, form a part 

 of the sixweeks grasses of the Southwest; B. curtipendula is widely distributed 

 and is much used for grazing and for hay; B. trijida is important from Texas 

 to Arizona. 



Spikelets not pectinately arranged (except in B. chondrosioides). the spikes falling entire at 

 maturity.. Section 1. Atheropogon. 



Spikelets pectinately arranged, the spikes persistent, the florets falling from the persistent 

 glumes Section 2. Chondrosium. 



Section 1. Atheropogon 



Plants annual 1. B. aristidoides. 



Plants perennial. 



Spikes usually 20 to 50; awns short, inconspicuous. 



Spikes of 1 or 2 spikelets; culms very slender 2. B. uniflora. 



Spikes of few to several spikelets; culms mostly stouter 3. B. curtipendula. 



Spikes fewer; awns conspicuous. 

 Glumes puhescent. 



Spikes rhomboid-oblong, as much as 2 cm. long, the spikelets somewhat pectinately 



arranged 6. B. chondrostoides. 



Spikes cuneate-triangular. about 1 cm. long (including the awns), the spikelets ap- 

 pressed, not pectinately arranged. 

 Culms 20 to 30 cm. tall; leaves crowded at base; spikes mostly 6 to 8. 



4. B. RIGIDISETA. 



Culms mostly 30 to 50 cm. tall, leafy throughout; spikes mostly more than 10. 



5. B. eludens. 

 Glumes glabrous or scabrous, not pubescent. 



Base of plants hard, rhizomatous; culms mostly simple; spikes 2 to 3 cm. long. 



7. B. RADICOSA. 

 Base of plants not rhizomatous; culms branching; spikes usually about 1.5 cm., some- 

 times 2 cm., long.. 8. B. filiformis. 



